DESCRIPTION (Investigator's Abstract): The present application's long- term objective is to extend fundamental knowledge about the neural control of individuated movements, those in which one body part moves relatively independently of the motion or posture of other body parts. Individuated movements i) are the first lost and last recovered when lesions affect the motor cortex or corticospinal tract; ii) play an increasingly important role in the motor repertoire of higher mammals, especially primates, in particular man; and iii) are used in many modes of cognitive expression, such as speaking (mouth) or playing a musical instrument (fingers). The proposed studies of individuated finger movements specifically aim to test two hypotheses. First,that generation of each individuated finger movement involves the activity of neurons distributed throughout the motor cortex (M1) hand area. Second, that some, but all, non primary cortical motor areas (NPMA) participate in visually-cued finger movement with each participating AMA making a different contribution, distinct from that of M1. To test these hypotheses, rhesus monkeys will be trained to perform visually-cued individuated movements of each finger of the right hand and of the wrist. As a trained monkey performs these movements, single neuron activity will be recorded in Ml and in concurrently with EMG activity from a number of muscles involved in the production of finger - movements. Spike -triggered averaging (SpTA) of EMG activity will be used to infer the strength of connections from each neuron to each muscle. These data on) each neurons's activity during finger movements and on its inferred connections to muscles will be incorporated in a model of the neural control of finger movements. Single neuron activity in different -As will be compared to distinguish the roles of these areas. Finally, Ml and NPMAI each will be reversibly inactivated by intracortical injection of the GABA agonist, muscimol, to determine: i) whether inactivation of different regions of the MI hand area impairs movements of different fingers, and ii) whether inactivation of different has different effects on visually-cued finger movements.